Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A photovoltaic module with reduced size is provided. The photovoltaic
module includes two wedged concentrator components and a solar cell
structure. The first wedged concentrator component is positioned on the
second wedged concentrator component. The solar cell structure is mounted
on a quadrilateral lateral surface of the first wedged concentrator
component for receiving light from the first wedged concentrator
component through the quadrilateral lateral surface. The wedge structure
of the concentrator components causes total internal reflection of the
light on a top surface of the first wedged concentrator component when
the light travels within the first wedged concentrator component from a
bottom surface to the quadrilateral lateral surface. A diffractive optics
element is provided in the second wedged concentrator component to
contribute the total internal reflection in the first wedged concentrator
component.

Claims:

1. A photovoltaic module, comprising: a first wedged concentrator
component having a first top surface and a first bottom surface arranged
unparallel with each other; a second wedged concentrator component having
a second top surface and a second bottom surface arranged unparallel with
each other, the first wedged concentrator component being positioned on
the second wedged concentrator component by placing the first bottom
surface on the second top surface; a solar cell structure mounted on a
quadrilateral lateral surface of the first wedged concentrator component
for receiving light from the first wedged concentrator component through
the quadrilateral lateral surface, wherein the light enters and leaves
the first wedged concentrator component through the first top surface and
the first bottom surface, respectively, enters and leaves the second
wedged concentrator component through the second top surface, further
enters the first wedged concentrator component through the first bottom
surface, and leaves the first wedged concentrator component through the
quadrilateral lateral surface in sequence, wherein total internal
reflection occurs on at least the first top surface when the light
travels within the first wedged concentrator component from the first
bottom surface to the quadrilateral lateral surface.

2. The photovoltaic module according to claim 1 wherein a gap is formed
between the first bottom surface and the second top surface, and the gap
is filled with a medium with an index of refraction less than the index
of refraction of the first and the second wedged concentrator components.

3. The photovoltaic module according to claim 1 wherein a diffractive
optics element is disposed on the second bottom surface to increase the
angle of the incidence when the light leaves the second wedged
concentrator component.

4. The photovoltaic module according to claim 1 wherein an
anti-reflective film is applied to the outside of the first top surface
for reducing reflection of the light when the light enters the first
wedged concentrator component through the first top surface.

5. The photovoltaic module according to claim 1 wherein an angle between
the quadrilateral lateral surface and the first bottom surface is an
acute angle.

6. The photovoltaic module according to claim 1 wherein the solar cell
structure comprises at least one solar cell for performing photovoltaic
conversion.

7. A photovoltaic module, comprising: a first wedged concentrator
component having a first top surface and a first bottom surface arranged
unparallel with each other; a second wedged concentrator component having
a second top surface and a second bottom surface arranged unparallel with
each other, the second top surface being adjacent to a first
quadrilateral lateral surface of the first wedged concentrator component;
a solar cell structure mounted on a second quadrilateral lateral surface
of the second wedged concentrator component for receiving light from the
second wedged concentrator component through the second quadrilateral
lateral surface thereof, wherein the light enters and leaves the first
wedged concentrator component through the first top surface and the first
quadrilateral lateral surface, respectively, and enters and leaves the
second wedged concentrator component through the second top surface and
the second quadrilateral lateral surface, respectively.

8. The photovoltaic module according to claim 7 wherein a gap is formed
between the first quadrilateral lateral surface and the second top
surface, and the gap is filled with a medium with an index of refraction
less than the index of refraction of the first and the second wedged
concentrator components.

9. The photovoltaic module according to claim 7 wherein a first
diffractive optics element is disposed on the first bottom surface to
increase an angle between the light path and the normal to the first
bottom surface.

10. The photovoltaic module according to claim 7 wherein a second
diffractive optics element is disposed on the second bottom surface to
increase an angle between the light path and the normal to the second
bottom surface.

11. The photovoltaic module according to claim 7 wherein an
anti-reflective film is applied to the outside of the first top surface
for reducing reflection of the light when the light enters the first
wedged concentrator component through the first top surface.

12. The photovoltaic module according to claim 7 wherein an angle between
the first quadrilateral lateral surface and the first bottom surface is
an acute angle.

13. The photovoltaic module according to claim 7 wherein an angle between
the second quadrilateral lateral surface and the second top surface is an
acute angle.

14. The photovoltaic module according to claim 7 wherein the solar cell
structure comprises at least one solar cell for performing photovoltaic
conversion.

15. A photovoltaic module, comprising: a first wedged concentrator
component having a first top surface and a first bottom surface arranged
unparallel with each other; a second wedged concentrator component having
a second top surface and a second bottom surface arranged unparallel with
each other, the first wedged concentrator component being positioned on
the second wedged concentrator component by placing the first bottom
surface on the second top surface; a third wedged concentrator component
having a third top surface and a third bottom surface arranged unparallel
with each other, the third top surface being adjacent to a first
quadrilateral lateral surface of the first wedged concentrator component;
a fourth wedged concentrator component having a fourth top surface and a
fourth bottom surface arranged unparallel with each other, the fourth top
surface being adjacent to the third bottom surface; a solar cell
structure mounted on a second quadrilateral lateral surface of the third
wedged concentrator component for receiving light from the third wedged
concentrator component through the second quadrilateral lateral surface,
wherein the light enters and leaves the first wedged concentrator
component through the first top surface and the first bottom surface,
respectively, enters and leaves the second wedged concentrator component
through the second top surface, enters and leaves the first wedged
concentrator component through the first bottom surface and the first
quadrilateral lateral surface, respectively, enters and leaves the third
wedged concentrator component through the third top surface and the third
bottom surface, respectively, enters and leaves the fourth wedged
concentrator component through the fourth top surface, and enters and
leaves the third wedged concentrator component through the third bottom
surface and the second quadrilateral lateral surface in sequence, wherein
total internal reflection occurs on at least the first top surface and
the third top surface when the light travels within the first wedged
concentrator component from the first bottom surface to the first
quadrilateral lateral surface and travels within the third wedged
concentrator component form the third bottom surface to the second
quadrilateral lateral surface.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to a photovoltaic module having a
concentrator, and more particularly to a photovoltaic module having a
wedged concentrator with reduced size and high concentration ratio.

BACKGROUND OF THE INVENTION

[0002] In recent years, renewable resource attracts great investment and
attention due to the overuse of non-renewable resource such as fossil
fuel and environmental protection issue. Solar energy is important
renewable resource which is clean, safe and abundant, compared with the
polluting fuel and hazardous nuclear energy. Solar cells (photovoltaic
cells) generate electrical power by converting solar radiation into
direct current electricity. The spectrum of sunlight includes visible
light, ultraviolet light (wavelength<400 nm) and infrared light
(wavelength>700 nm). For this wavelength range, materials presently
used for photovoltaics include silicon material such as monocrystalline
silicon, polycrystalline silicon and amorphous silicon, which have better
photovoltaic effect. Among the silicon materials, monocrystalline has the
best conversion efficiency but the highest cost. On the other hand, the
polycrystalline silicon is of less efficiency, but is less expensive to
produce in bulk.

[0003] A solar cell may include a PN junction with a large surface area.
The generation of electric current happens inside the depletion zone of
the PN junction. When a photon of light, carrying energy higher than the
energy gap required to activate an atom from the valence band to the
conduction band, is absorbed by an atom in the N-type silicon, it will
dislodge an electron to create a free electron and a hole. The free
electrons and holes flow between the cathode and the anode to provide the
electric current.

[0004] The performance of the solar cell depends on the photovoltaic
efficiency of the solar cell. With the development of various
semiconductor processes, the efficiency of the solar cells is much
improved. For example, III-V material such as GaAs material has some
electronic and material properties which are superior to those of
silicon. Furthermore, GaAs material has direct band gap and can absorb
the sunlight photons more efficiently. Hence, great emphasis is put on
high efficiency GaAs solar cell. For cost consideration, thin-film solar
cells are also rapidly growing. Furthermore, solar tracker systems are
developed to assist the solar cells to automatically follow the sun
during the course of a day and throughout the seasons of the year so as
to generate more energy than conventional fixed approaches.

[0005] Other than the above-mentioned approaches, how to collect more
sunlight is another issue to increase the energy output of the solar
cells or the photovoltaic cells. Since the solar cells can only receive
incident light with limited angle of incidence, the photovoltaic module
is usually designed as a large area panel and a solar cell array is
arranged in the panel to receive most of the nearly normal incident
light. In other to reduce the size of the panel and the quantity of the
solar cells, a concentrator is provided in the photovoltaic module to
collect non-normal incident light to increase the efficiency. Several
documents or patents such as US 2007/0095385 A1, TWM361103, TWM350025 and
TWM360983 proposed several structures of the photovoltaic modules.

[0006] Please refer to FIG. 1, a schematic diagram illustrating the
structure of a conventional photovoltaic module. The photovoltaic module
1 includes a concentrating structure 10 and a solar cell array 11. The
concentrating structure 10 employs a condensing lens 12 to refract and
focus light. The central incident light is focused on the main area A,
while the other incident light is reflected and compensated by a
plurality of compensating elements 13 to reach the main area A.
Therefore, the concentrating effect is enhanced. The solar cell array 11
located at the main area A under the condensing lens 12 receives the
focused, refracted or reflected light and performs photovoltaic
conversion to generate electrical power.

[0007] The above-described concentrating structure 10 can change the light
paths of the incident light to allow the incident light to reach limited
area. Hence, the size or number of the solar cells of the solar cell
array 11 can be reduced. The photovoltaic module 1, however, has
considerably large size due to the thick concentrating structure 10.
Furthermore, the concentrating effect is also affected when the incident
direction of the light is gradually changed during the sun's movement.
Such concentrating structure 10 cannot collect and transmit most sunlight
to the main area A all the time.

[0008] Therefore, there is a need of providing a photovoltaic module with
reduced size and high concentration ratio in order to obviate the
drawbacks encountered from the prior art.

SUMMARY OF THE INVENTION

[0009] In accordance with an aspect of the present invention, there is
provided a photovoltaic module. The photovoltaic module includes two
wedged concentrator components and a solar cell structure. The first
wedged concentrator component has a first top surface and a first bottom
surface arranged unparallel with each other, while the second wedged
concentrator component has a second top surface and a second bottom
surface arranged unparallel with each other. The first wedged
concentrator component is positioned on the second wedged concentrator
component by placing the first bottom surface on the second top surface.
The solar cell structure is mounted on a quadrilateral lateral surface of
the first wedged concentrator component for receiving light from the
first wedged concentrator component through the quadrilateral lateral
surface. At first, the light enters and leaves the first wedged
concentrator component through the first top surface and the first bottom
surface, respectively. Then, the light enters and leaves the second
wedged concentrator component through the second top surface. The light
enters the first wedged concentrator component again through the first
bottom surface, and leaves the first wedged concentrator component
through the quadrilateral lateral surface. Total internal reflection
occurs on at least the first top surface when the light travels within
the first wedged concentrator component from the first bottom surface to
the quadrilateral lateral surface. At last, the light is received by the
solar cell structure mounted on the quadrilateral lateral surface of the
first wedged concentrator component.

[0010] In accordance with another aspect of the present invention, there
is provided another photovoltaic module. The photovoltaic module includes
two wedged concentrator components and a solar cell structure. The first
wedged concentrator component has a first top surface and a first bottom
surface arranged unparallel with each other, while the second wedged
concentrator component has a second top surface and a second bottom
surface arranged unparallel with each other. The second wedged
concentrator component is located beside the first wedged concentrator
component, and the second top surface is adjacent to a first
quadrilateral lateral surface of the first wedged concentrator component.
The solar cell structure is mounted on a second quadrilateral lateral
surface of the second wedged concentrator component for receiving light
from the second wedged concentrator component through the second
quadrilateral lateral surface. At first, the light enters and leaves the
first wedged concentrator component through the first top surface and the
first quadrilateral lateral surface, respectively. Then, the light enters
and leaves the second wedged concentrator component through the second
top surface and the second quadrilateral lateral surface, respectively.
At last, the light is received by the solar cell structure mounted on the
second quadrilateral lateral surface of the second wedged concentrator
component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above contents of the present invention will become more
readily apparent to those ordinarily skilled in the art after reviewing
the following detailed description and accompanying drawings, in which:

[0012] FIG. 1 is a schematic diagram illustrating the structure of a
conventional photovoltaic module;

[0013]FIG. 2A is a perspective view illustrating a first embodiment of a
photovoltaic module according to the present invention;

[0017]FIG. 3c is a top view of the photovoltaic module of FIG. 3A
illustrating the light path;

[0018]FIG. 4 is a perspective view illustrating a third embodiment of a
photovoltaic module according to the present invention; and

[0019]FIG. 5 is a perspective view illustrating a photovoltaic module
obtained by modifying the photovoltaic module of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] The present invention will now be described more specifically with
reference to the following embodiments. It is to be noted that the
following descriptions of preferred embodiments of this invention are
presented herein for purpose of illustration and description only. It is
not intended to be exhaustive or to be limited to the precise form
disclosed.

[0021] From above description, the solar cell (photovoltaic cell) usually
works together with concentrator(s) to enhance light-collecting
efficiency and conversion efficiency. According to the conventional
design, the concentrator usually faces toward the same direction as the
solar cell (photovoltaic cell). In other words, the main incident
direction of the light to be collected is substantially vertical to the
light-receiving surface of the solar cell. It is called as "coaxial". The
light entering the concentrator is reflected or focused so as to be
transmitted to the designation area. To achieve the desired
light-collecting efficiency, the size or the thickness of the
concentrator cannot be reduced due to the concentrator.

[0022] According to the present invention, the solar cell is located on
the lateral surface of the concentrator. In other words, the concentrator
does not face toward the same direction as the solar cell. The light
entering the concentrator is reflected to pass the lateral surface. In
addition to enhancing the light-collecting efficiency, the size or
thickness of the photovoltaic cell may be reduced. The special structure
of the concentrator is illustrated as follows.

[0023] Please refer to FIG. 2A, a perspective view illustrating a first
embodiment of a photovoltaic module according to the present invention.
The photovoltaic module 20 includes two wedged concentrator components 21
and 22. In an embodiment, the first wedged concentrator component 21
includes a top surface A11 and a bottom slant surface A12 opposite to
each other in an unparallel manner and lateral surfaces, while the second
wedged concentrator component 22 includes a top slant surface A21 and a
bottom surface A22 opposite to each other in an unparallel manner and
lateral surfaces. The first wedged concentrator component 21 is
positioned on the second wedged concentrator component 22 by placing the
bottom slant surface A12 of the first wedged concentrator component 21 on
the top slant surface A21 of the second wedged concentrator component 22.
There is a gap 200 formed between the bottom slant surface A12 and the
top slant surface A21.

[0024] The wedged concentrator components 21 and 22 are made of
transparent material such as glass. A diffractive optics element A220 is
disposed on the bottom surface A22 of the second wedged concentrator
component 22. The surfaces of the wedged concentrator components 21 and
22 are coated or covered with high reflectance material except for the
light path, i.e. the top surface A11, the bottom slant surface A12, the
quadrilateral lateral surface A13 and the top slant surface A21. Although
the transparent top surface A11 of the first wedged concentrator
component 21 is capable of receiving the incident light, scatter
phenomenon always occurs. To avoid possible reflection by the top surface
A11, an anti-reflective film (not shown) is optionally applied to the
outside of the top surface A11 to reduce photon loss due to reflection.

[0025] The photovoltaic module 20 further includes a solar cell structure
25 mounted on the lateral surface A13 of the first wedged concentrator
component 21 for performing photovoltaic conversion. The solar cell
structure 25 includes at least a solar cell. The design, property or
function of the solar cell is similar to the conventional photovoltaic
module. For example, monocrystalline silicon, polycrystalline silicon,
amorphous silicon, or GaAs solar cell is applicable. The quantity of the
solar cells is determined according to the size of the lateral surface
A13 of the first wedged concentrator component 21.

[0026] In this embodiment, the top surface A11 faces toward and receives
the sunlight. The incident light will be refracted or reflected by the
surfaces of the wedged concentrator components 21 and 22, and thus reach
the lateral surface A13. Then, the solar cell structure 25 receives the
collected light and performs photovoltaic conversion to generate
electrical power. It is to be noted that reflection and refraction of the
light occur based on the dimension, angle between surfaces or material of
the wedged concentrator components 21 and 22. In this embodiment, the
related surfaces are smooth surfaces without curvature.

[0027] As described above, the wedged concentrator component has two
unparallel surfaces to direct and condense the light therebetween, e.g.
the top surface A11 and the bottom slant surface A12 of the first wedged
concentrator component 21. In particular, there is an acute angle
θA between the lateral surface A13 and the bottom slant
surface A12. The top surface A11 may be perpendicular to the four lateral
surfaces, but not limited to this condition. The second wedged
concentrator component 22 has the similar structure. In this embodiment,
the two wedged concentrator components 21 and 22 have similar dimension,
but are not limited to this condition. The condensing effect of the
photovoltaic module 20 depends on the acute angle θA between
the lateral surface A13 and the bottom slant surface A12.

[0028] Please refer to FIG. 2B, a side view of the photovoltaic module 20
of FIG. 2A. The light with angle of incidence θi0 enters the
first wedged concentrator component 21 through the top surface A11. The
light direction is changed and the angle of refraction is θf0.
Then, the refracted light reaches the bottom slant surface A12. Since the
gap 200 between the bottom slant surface A12 and the top slant surface
A21 is usually filled with gas or other medium with low index of
refraction, the light will pass through the bottom slant surface A12 and
the top slant surface A21 to enter the second wedged concentrator
component 22 and reach the bottom surface A22 with an angle of incidence
θi1. The light path in the first wedged concentrator component
21 is parallel to that in the second wedged concentrator component 22
under the condition that the two wedged concentrator components 21 and 22
are made of the same material. The angle of incidence θi1 is
equivalent to the angle of refraction θf0 when the top surface
A11 and the bottom surface A22 are parallel with each other.

[0029] In an embodiment, the diffractive optics element A220 on the bottom
surface A22 is a periodic grating structure in micrometer dimension with
high reflectance. The periodic grating structure may have rectangular or
triangular profile, and the spacing of the periodic grating structure
depends on the wavelength of the light. Most of the light emitted to the
periodic grating structure is diffracted with angle larger than the angle
of reflection. That is, the periodic grating structure can increase the
angle of reflection. For example, a portion of the light is sent back to
the top slant surface A21 with an angle θd1 deviating from the
normal to the bottom surface A22. The angle θd1 is greater
than the angle of incidence θi1. Then, the light sequentially
passes through the top slant surface A21, the gap 200 and the bottom
slant surface A12 with refraction. The light reaches the top surface A11
with an angle of incidence θi2. As explained above, the light
path in the second wedged concentrator component 22 is parallel to that
in the first wedged concentrator component 21, and the angle of incidence
θi2 is equivalent to the angle θd1 which is greater
than the angle of refraction θf0.

[0030] In this embodiment, the angle of incidence θi2 is
greater than the critical angle for the boundary between the top surface
A11 and the surrounding gas (or other specific medium with low index of
refraction) and total internal reflection happens. Due to the wedge
structure of the concentrator component 21, the next angle of incidence
is greater than the previous angle of incidence along the light path,
i.e. θi2=θr2<θi3=θr3< .
. . Therefore, the angle of incidence is always greater than the critical
angle to ensure total internal reflection. After several total internal
reflections, the light is successfully collected to the lateral surface
A13 so that the solar cell structure 25 may receive the most light
photons.

[0031] Please refer to FIG. 3A, a perspective view illustrating a second
embodiment of a photovoltaic module according to the present invention.
The photovoltaic module 30 includes two wedged concentrator components 31
and 32. In this embodiment, the first wedged concentrator component 31
includes a top surface B11 and a bottom surface B12 opposite to each
other in unparallel manner, while the second wedged concentrator
component 32 includes a top surface B21 and a bottom slant surface B22
opposite to each other in unparallel manner. The second wedged
concentrator component 32 is laid on one lateral side and positioned
beside the first wedged concentrator component 31. The top surface B21 is
made to be adjacent to a quadrilateral lateral surface B13 of the first
wedged concentrator component 31. There is a gap 300 formed between the
top surface B21 and the lateral surface B13.

[0032] As described with reference to FIG. 2, the wedged concentrator
components 31 and 32 may be made of transparent material such as glass.
Furthermore, in this embodiment, diffractive optics elements B120 and
B220 are disposed on the bottom slant surfaces B12 and B22 of the first
wedged concentrator component 31 and the second wedged concentrator
component 32, respectively. The surfaces of the wedged concentrator
components 31 and 32 are coated or covered with high reflectance material
except for the light path, i.e. the top surface B11, the quadrilateral
lateral surface B13, the top surface B21 and the quadrilateral lateral
surface B23. An anti-reflective film (not shown) is optionally applied to
the outside of the top surface B11 to reduce reflection and scatter
phenomenon.

[0033] The photovoltaic module 30 further includes a solar cell structure
30 mounted on the quadrilateral lateral surface B23 of the second wedged
concentrator component 32 for performing photovoltaic conversion. The
solar cell structure 35 includes at least a solar cell. The design,
property or function of the solar cell is similar to the conventional
photovoltaic module. For example, monocrystalline silicon,
polycrystalline silicon, amorphous silicon, or GaAs solar cell is
applicable. The quantity of the solar cells is determined according to
the size of the quadrilateral lateral surface B23 of the second wedged
concentrator component 32. Compared to the photovoltaic module 20 in the
first embodiment, the present photovoltaic module 30 having
lateral-to-top combination of the wedged concentrator components 31 and
32 has better condensing efficiency. Therefore, the area of the solar
cell structure 35 or the quantity of the solar cells can be further
reduced.

[0034] In this embodiment, the top surface B11 faces toward and receives
the sunlight. The incident light will be refracted or reflected by the
surfaces of the wedged concentrator components 31 and 32, and thus reach
the lateral surface B23. Then, the solar cell structure 35 receives the
collected light and performs photovoltaic conversion to generate
electrical power. The design of the unparallel surfaces B11 and B12 and
the unparallel surfaces B21 and B22 may direct and restrict the light in
the wedged concentrator components 31 and 32 with very little loss. In
this embodiment, there is an acute angle θB between the
lateral surface B13 and the bottom surface B12. The top surface B11 may
be perpendicular to the four lateral surfaces, but not limited to this
condition. The second wedged concentrator component 32 has the similar
structure. There is an acute angle, may be equivalent to the acute angle
θB, between the lateral surface B23 and the top surface B21.
The angle between the lateral surface B13 and another lateral surface B14
may be supplementary angle of angle θB. The condensing effect
of the photovoltaic module 30 depends on the acute angle θB.

[0035] Please refer to FIG. 3B, a side view of the photovoltaic module 30
of FIG. 3A. The light with angle of incidence θi0, greater
than that described in the first embodiment, enters the first wedged
concentrator component 31 through the top surface B11. The light
direction is changed and the angle of refraction is θf0. Then,
the refracted light reaches the bottom surface B12. In this embodiment,
most of the light emitted to the bottom surface B12 is diffracted by the
diffractive optics element B120 with angle larger than the angle of
reflection. That is, the diffractive optics element B120 such as periodic
grating structure can increase the angle of reflection. For example, a
portion of the light is sent back to the top surface B11 with an angle
θd1 deviating from the normal to the bottom surface B12. The
angle θd1 is greater than the angle of incidence
θi1. The light reaches the top surface B11 with an angle of
incidence θi2. In this embodiment, the angle of incidence
θi2 is greater than the critical angle for the boundary
between the top surface B11 and the surrounding gas (or other medium with
low index of refraction) and total internal reflection with angle of
reflection θr2 happens. Due to the wedge structure of the
concentrator component 31, the next angle of incidence is greater than
the previous angle of incidence along the light path. Therefore, the
angle of incidence is always greater than the critical angle to ensure
total internal reflection. The light sequentially passes through the
lateral surface B13, the gap 300 and the top surface B21 with refraction
and then enters the second wedged concentrator component 32.

[0036] In this embodiment, total internal reflection happens once before
the light enters the second wedged concentrator component 32. However,
the times of the total internal reflection are not limited. If the
initial angle of incidence θi1 is smaller or the angle
θB between the lateral surface B13 and the bottom surface B12
is greater, the times increase. Alternatively, if the diffractive optics
element B120 may cause greater θd1, the initial angle of
incidence θi1 is greater or the angle θB is
smaller, the light will directly reach the lateral surface B13 without
being reflected by the top surface B11.

[0037] Please refer to FIG. 3c, a top view of the photovoltaic module 30
of FIG. 3A, illustrating the light path in the second wedged concentrator
component 32. The light with angle of incidence θi3 reaches
the bottom surface B22. In this embodiment, most of the light emitted to
the bottom surface B22 is diffracted by the diffractive optics element
B220 with angle larger than the angle of reflection. That is, the
diffractive optics element B220 such as periodic grating structure can
increase the angle of reflection. For example, a portion of the light is
sent back to the top surface B21 with an angle θd2 deviating
from the normal to the bottom surface B22. The angle θd2 is
greater than the angle of incidence θi3. The light reaches the
top surface B21 with an angle of incidence θi4. In this
embodiment, the angle of incidence θi4 is greater than the
critical angle for the boundary between the top surface B21 and the
surrounding gas, and total internal reflection with angle of reflection
θr4 happens. After several total internal reflections, the
light is successfully collected to the lateral surface B23 so that the
solar cell structure 35 may receives the most light photons.

[0038] In this embodiment, total internal reflection happens once before
the light is received by the solar cell structure 35. However, since the
light passes the top surface B21 from different directions, i.e. the
angle of incidence θi3 varies, the design of the diffractive
optics element B220 may be changed to modify the angle θd2.
Alternatively, the design of the angle θB may be adjusted to
increase or reduce the times of the total internal reflections within the
second wedged concentrator component 32.

[0039] Please refer to FIG. 4, a perspective view illustrating a third
embodiment of a photovoltaic module according to the present invention.
The photovoltaic module 40 includes four wedged concentrator components
41, 42, 43 and 44. In this embodiment, the wedged concentrator components
41, 42, 43 and 44 include unparallel surfaces C11 and C12, C21 and C22,
C31 and C32, and C41 and C42, respectively. The first wedged concentrator
component 41 is positioned on the second wedged concentrator component 42
by placing the surface C12 on the surface C21. The third wedged
concentrator component 43 is laid on one lateral side and positioned
beside the first wedged concentrator component 41, and the surface C31 is
made to be adjacent to a quadrilateral lateral surface C13 of the first
wedged concentrator component 31. The fourth wedged concentrator
component 44 is laid on one lateral side and positioned beside the third
wedged concentrator component 43 and the surface C41 is made to be
adjacent to the surface C32 of the third wedged concentrator component
43. There are gaps 401, 402 and 403 formed between the surfaces C12 and
C21, surfaces C13 and C31, and surfaces C41 and C32, respectively. A
solar cell structure 45 is mounted on a quadrilateral lateral surface C33
of the third wedged concentrator component 43. Two diffractive optics
elements C220 and C420 are disposed on the surfaces C22 and C42,
respectively.

[0040] This embodiment combines the designs of the first embodiment and
the second embodiment of the photovoltaic modules 20 and 30. Concretely,
the combination of the first wedged concentrator component 41 and the
second wedged concentrator component 42 has the same operation principle
as the combination of the first wedged concentrator component 21 and the
second wedged concentrator component 22 in the first embodiment, so does
the combination of the third wedged concentrator component 43 and the
fourth wedged concentrator component 44. Furthermore, the combination of
the first wedged concentrator component 41 and the third wedged
concentrator component 43 has the same operation principle as the
combination of the first wedged concentrator component 31 and the second
wedged concentrator component 32 in the second embodiment. In conclusion,
the light passes the four wedged concentrator components 41, 42, 43 and
44 with refraction, diffraction, and total internal reflection to reach
the solar cell structure 45 and achieve the light-collecting purpose.

[0041] The third embodiment may be further modified by adding wedged
concentrator components. Please refer to FIG. 5 illustrating a modified
photovoltaic module 50. A small scale photovoltaic module with similar
structure of the photovoltaic module 40 is provided. That is, the small
scale photovoltaic module has four wedged concentrator components
arranged in the above-described manner. The small scale photovoltaic
module is attached to the quadrilateral lateral surface C33 of the third
wedged concentrator component 43 of the large size photovoltaic module
40. Compared with the photovoltaic module 40 in the third embodiment, the
modified photovoltaic module 50 has better concentrating effect so that a
more compact solar cell structure 55 is employed. Hence, fewer solar
cells are required in the solar cell structure 55 and the cost thereof
can be further reduced.

[0042] In conclusion, the photovoltaic modules according to the present
invention take advantage of wedged concentrator components and
diffractive optics elements to change the light path to enhance the
concentrating effect. The enhancement also improves the total conversion
efficiency. Furthermore, the photovoltaic modules according to the
present invention significantly reduce the thickness and the size thereof
and it is not necessary to mount the solar cells to face toward the
sunlight by changing the light path. The quantity of the solar cells may
be reduced because the required effective receiving area for the sunlight
is not as large as that of the conventional photovoltaic module. Contrary
to the prior arts, the photovoltaic module according to the present
invention may transmit incident light with a great range of incident
angles to the solar cell structure without tracking the sun. Therefore,
the photovoltaic module has better performance concerning size, cost and
conversion efficiency.

[0043] While the invention has been described in terms of what is
presently considered to be the most practical and preferred embodiments,
it is to be understood that the invention needs not to be limited to the
disclosed embodiment. On the contrary, it is intended to cover various
modifications and similar arrangements included within the spirit and
scope of the appended claims which are to be accorded with the broadest
interpretation so as to encompass all such modifications and similar
structures.